for BLE Nano v2

Revision:
0:5f632ba61cb5
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Sun Sep 24 09:49:58 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#ca661f9d28526ca8f874b05432493a489c9671ea